1. Field
The present invention relates to a multi-step press system and, more particularly, to a multi-step press system for simultaneously press-forming workpieces placed on a plurality of press-forming stations through a single pressing stroke.
2. Discussion of the Related Technology
A press refers to a machine for manufacturing products by shearing, forming and squeezing a material such as a metal plate, a plastic, a fiber and the like. The press is suitable for use in mass production of articles and finds extensive applications in a variety of industrial fields. Press die sets of varying structures are employed in the press for the purpose of cutting, punching, blanking, piercing, bending, drawing and embossing workpieces. Each of the press die sets includes an upper die attached to a ram of the press and a lower die secured to a table thereof. The press die sets are often called a punch, a cutter or other names depending on the functions performed by them.
Arrangements that achieve automatic workpiece loading and unloading operations for improvement of productivity in a press are disclosed in Korean Patent Registration Publication No. 10-346866 and U.S. Pat. No. 6,105,414. The arrangements taught in these prior art references are of the type capable of loading and unloading workpieces by the actuation of a transfer feeder.
However, these arrangements involve many difficulties in adapting themselves to a multi-step press system that sequentially loads workpieces into a plurality of press-forming stations and then press-forms them into final products. Specifically, there is a problem in that the transfer feeder for sequentially loading the workpieces into each of the press-forming stations is structurally complex. Another problem is that a lot of dead time is spent in loading and unloading the workpieces, which in turn leads to reduced manufacturing speed, low productivity and increased production costs.
In the meantime, there is known a multi-step press system whose press die is comprised of a plurality of transfer dies corresponding to press-forming stations, each of the transfer dies having a set of upper and lower die members. Such a press die arrangement is disclosed in Korean Patent Laid-open Publication No. 2000-70458 wherein an upper die member and a lower die member are removably attached to a die holder by means of a clamp. However, this poses a problem in that press die fabrication costs are increased due to the use of the die holder for clamping the upper die member and the lower die member. Another problem is that the task of attaching and removing the upper die member and the lower die member in individual press-forming stations are time-consuming, labor-intensive and costly.
The discussion in this section is to provide general background information, and does not constitute an admission of prior art.